A conventional mold-BGA-type semiconductor device is, as shown in FIGS. 1A and 1B, structured by adhering a buffering elastic material called elastomer 10 onto the surface of a chip 1, thermo-compression-bonding a copper wiring 12 to a pad 2 of the chip 1, sealing with a sealant 13. FIG. 1A shows a state that the pad 2 is disposed at the center of the chip 1, and FIG. 1B shows a state that it is disposed peripherally.
Also, Japanese patent application laid-open Nos. 3-94438 (1991) and 8-204062 (1996) disclose examples of mold-BGA-type semiconductor devices where solder balls are disposed on the surface of resin package on the front-face side of semiconductor chip.
As one example of them, the semiconductor device disclosed in Japanese patent application laid-open No. 3-94438 (1991) is shown in FIGS. 2A and 2B. FIG. 2A is a cross sectional view showing the semiconductor device before forming the solder balls, and FIG. 2B is a cross sectional view showing the semiconductor device after forming the solder balls.
As shown in FIG. 2A, it is fabricated by forming a dummy support 15 uniting with a die pad 14 on which a semiconductor chip 1 is to be mounted, adhering the semiconductor chip 1 onto the die pad 14, bonding between the pad 2 of the semiconductor chip 1 and the dummy support 15 through a wire 5 (metal thin wire), resin-sealing the whole members. After resin-sealing, as shown in FIG. 2B, outsides from the line B-B' and line C-C' in FIG. 2A are cut down and separated, thereby allowing part where the semiconductor chip 1 is mounted to be remaining. The surface of the remaining part and the wire 5 are polished to expose the surface of wire 5 until having a predetermined thickness. Solder balls 6 are formed on the exposed and polished part of the wire 5.
However, in the BGA-type semiconductor device in FIGS. 1A and 1B, there are the problems that the cost for material becomes expensive because the wiring structure from the pad 2 to the solder ball 6 uses a polyimide tape 11 and the elastomer 10, and that the fabrication process is complicated because of the adhering structure.
Also, in the BGA-type semiconductor device in FIGS. 2A and 2B, there is the problem that the cost for material becomes expensive because the dummy support 15 is used.